Hi Martin, Insert uses solid/extended offsetting and there are a lot of situations where the extension mechanism in the geometry library can just get confused.

So I wouldn't be surprised if you're running into some limitation involving offsetting more than any particular problem that you are doing wrong yourself. I will take a look at your file and your screencast though to see if I can give you any tips.

Basically though Inset tries to bundle up several offset and boolean operations and if it is not able to get a result for you, you may need to do some a more sort of "low level" construction method constructing individual pieces or surfaces yourself by stuff like offsetting only one surface at a time and building extension areas manually, etc...

And when you get something that looks weird like that with surface pieces kind of "leaking" out into hole areas or past outer boundaries, it means that the geometry has some kind of mangled trim boundaries, either some edges of the boundary missing, or mangled in some way like with pieces crossing over each other or things like that.

In this case it's some bug in inset or in something that inset uses that is making the mangled result. I'll put it on my list to see if it's possible for me to fix it up or at least figure out which area the bug is at.

Thanks for checking this out - I'm glad to have brought this to your attention and relieved I was doing things properly.
After playing around with it for a while, I can see that Inset is nice to have in the MoI toolbox, I can see me using it quite a lot.

Is there any reason that a zero value entered into the 'Thickness' property couldn't be made to work - I'm thinking that it might be a way of offsetting an entire surface by the amount entered into the 'Use separate height' property?

> Is there any reason that a zero value entered into the 'Thickness' property couldn't be made to work
> - I'm thinking that it might be a way of offsetting an entire surface by the amount entered into
> the 'Use separate height' property?

If I understand you properly, you can instead use the Construct > Offset command to generate that kind of full surface offset.

> It probably isn't important, but this is just to let you know that the conrod.3dm
> test file I supplied seems to works OK in MoI v2.

Ah, thanks for testing in v2 as well - I have taken some updates to the geometry library in v3 and there seems to be some change that has broken a couple of things that used to work before, I am going to be trying to track that down to fix it. I think it has something to do with calculating intersections involving cylinders.

> Is there any reason that a zero value entered into the 'Thickness' property couldn't be made to work
> - I'm thinking that it might be a way of offsetting an entire surface by the amount entered into
> the 'Use separate height' property?

"If I understand you properly, you can instead use the Construct > Offset command to generate that kind of full surface offset."

Hi Michael.

What I had in mind was that it could be used to alter the thickness or width etc of the part and keep it as a solid, rather than offset a separate surface from that solid - I suppose it would be the equivalent of an 'offset face' operation in other software.

This notion came about as a natural progression from playing around with Inset.
Whilst trying to find the cause of my problem, I just kept reducing the Thickness setting until I reached the point where zero was the only place left to go :-)

Offsetting the face of a solid to allow it to shrink or grow feels like it could be worth having somewhere in MoI - it'd be great ( for me) for tweaking hole and slot sizes, for instance.

Sorry Michael, but I couldn't follow this bit:- "You can get the basics of it right now by using Edit > Separate on the face, then doing a shell, then deleting the bottom face of the shell and then joining it back in." I'm probably having a blonde moment though, but thoroughly enjoying using MoI.

> Sorry Michael, but I couldn't follow this bit:- "You can get the basics of it right now by using
> Edit > Separate on the face, then doing a shell, then deleting the bottom face of the shell and
> then joining it back in." I'm probably having a blonde moment though, but thoroughly
> enjoying using MoI.

Those are just the steps you can do currently to get the same result as what I think you're looking for with the "zero width" inset.

Step 1 - select the face of the solid that you wanted to do the inset on.

Step 2 - run Edit > Separate to break that face off from the main object and make it into its own separate individual surface. This is because the Shell command in the next step operates differently depending on whether you have an unjoined individual surface selected or whether you have a face selected that is joined to other things.

Step 3 - Run Construct > Offset > Shell on the separated surface. When run on a surface shell thickens a surface into a slab.

So now at this point you basically have all the pieces that you were looking for, the only problem is that the shelled surface is a solid with top and bottom caps, so in order to finish it up you will want to delete the bottom face of this solid slab piece and then with the bottom open you can join the main body and the thickened slab piece together again.

In order to get at the bottom face of the slab you will probably want to hide the main piece temporarily. One quick way to do that is by using the "isolate" functionality - select the slab and right-click on the Hide button. Doing a right-click does an "Isolate" operation which keeps the selected object and instead hides everything else. Then when you're done working on that object, do second right-click on the Hide button and it will restore object visibility to the previous state before you did the initial Isolate.

Hi Martin, so after a whole bunch of testing and debugging I was finally able to track down the bug that was making your original 1mm inset here fail, it was a bug in the latest update to the geometry library.

So I've got that fixed now so the next v3 beta will be able to do that inset again ok.